全文获取类型
收费全文 | 5958篇 |
免费 | 356篇 |
出版年
2023年 | 14篇 |
2022年 | 53篇 |
2021年 | 111篇 |
2020年 | 75篇 |
2019年 | 89篇 |
2018年 | 132篇 |
2017年 | 117篇 |
2016年 | 187篇 |
2015年 | 280篇 |
2014年 | 284篇 |
2013年 | 455篇 |
2012年 | 523篇 |
2011年 | 458篇 |
2010年 | 261篇 |
2009年 | 268篇 |
2008年 | 334篇 |
2007年 | 346篇 |
2006年 | 298篇 |
2005年 | 287篇 |
2004年 | 288篇 |
2003年 | 278篇 |
2002年 | 248篇 |
2001年 | 52篇 |
2000年 | 49篇 |
1999年 | 57篇 |
1998年 | 61篇 |
1997年 | 35篇 |
1996年 | 52篇 |
1995年 | 33篇 |
1994年 | 52篇 |
1993年 | 24篇 |
1992年 | 39篇 |
1991年 | 32篇 |
1990年 | 27篇 |
1989年 | 26篇 |
1988年 | 23篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 20篇 |
1984年 | 36篇 |
1983年 | 20篇 |
1982年 | 27篇 |
1981年 | 22篇 |
1980年 | 23篇 |
1979年 | 17篇 |
1978年 | 18篇 |
1977年 | 23篇 |
1976年 | 18篇 |
1975年 | 17篇 |
1973年 | 17篇 |
排序方式: 共有6314条查询结果,搜索用时 171 毫秒
151.
Giuseppe Battistoni Fabrizio Cappucci Nicola Bertolino Maria Grazia Brambilla Hae Song Mainardi Alberto Torresin 《Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB)》2013,29(6):656-661
The purpose of this work is to investigate the capability of the FLUKA Monte Carlo (MC) code to simulate the Elekta Leksell Gamma Knife Perfexion (LGK-PFX) and reproduce the Treatment Planning System (TPS) Leksell GammaPlan version 8.2 (LGP) dose calculations for the case of a water equivalent phantom target. Thanks to the collaboration with Elekta Instruments AB, the collimation system geometry, the source positions and all the involved material have been simulated in detail. The relative linear dose distribution along the three coordinate axes, for each collimator size, and the Relative Output Factors (ROF) have been investigated. The simulation has been validated comparing simulated linear dose profiles with measurements performed with EBT radiochromic films. The acceptance criterion between experimental data and FLUKA results is based on the gamma index (GI) method. The FLUKA MC calculation for the ROF provided the values of 0.920 for the 8 mm collimators and 0.800 for the 4 mm collimators. These values are in good agreement with the Elekta reference data of 0.924 and 0.805 respectively. The percentage difference between calculated and reference values for the ROF is under 1% and within the FLUKA uncertainty. Also the simulated relative dose profiles show a good agreement with the LGP calculation expressed by means of the gamma index method. This established accuracy proves that FLUKA is a suitable and powerful tool in order to reproduce successfully the LGP calculations for the homogeneous media. 相似文献
152.
Giuseppe Giaccone 《Plant biosystems》2013,147(3):217-222
Abstract Phytobenthos from Eastern Mediterranean Sea. — The A. states the results of an exploration, by diving techniques, in the Eastern Mediterranean Sea, along 13 stations located in the midle-western and southern region of the Aegean Sea. Besides to the values of various ecology elements (saltness, brightness, nutrition salts), informations about reologic regime in the Aegean Sea are reported. It has been collected 175 floral entities, with the following per cent composition: Chlorophyceae 14,5%, Phoeophyceae 17,0%, Rhodophyceae 68,3%. Eastern Mediterranean Sea underwater flora presents in the explored stations a R/P index equal to 4, which characterizes it as a subtropical one. 相似文献
153.
Valentina Gambino Giulia De Michele Oriella Venezia Pierluigi Migliaccio Valentina Dall'Olio Loris Bernard Simone Paolo Minardi Maria Agnese Della Fazia Daniela Bartoli Giuseppe Servillo Myriam Alcalay Lucilla Luzi Marco Giorgio Heidi Scrable Pier Giuseppe Pelicci Enrica Migliaccio 《Aging cell》2013,12(3):435-445
154.
Fabio Casu Rebecca K. Harston Maria A. Chiacchio Giuseppe Gumina 《Nucleosides, nucleotides & nucleic acids》2013,32(3):224-235
2′-Modified inosine analogs have been synthesized from 6-chloropurine riboside via 6-dimethylaminopurine or 6-benzyloxypurine intermediates. The dimethylaminopurine intermediate was obtained via an unusually facile dimethylamine transfer from dimethylformamide. Graphical Abstract: 相似文献
155.
Tiziana Cabras Elisabetta Pisano Caterina Montaldo Maria Rita Giuca Federica Iavarone Giuseppe Zampino Massimo Castagnola Irene Messana 《Molecular & cellular proteomics : MCP》2013,12(7):1844-1852
People with Down syndrome, a frequent genetic disorder in humans, have increased risk of health problems associated with this condition. One clinical feature of Down syndrome is the increased prevalence and severity of periodontal disease in comparison with the general population. Because saliva plays an important role in maintaining oral health, in the present study the salivary proteome of Down syndrome subjects was investigated to explore modifications with respect to healthy subjects. Whole saliva of 36 Down syndrome subjects, divided in the age groups 10–17 yr and 18–50 yr, was analyzed by a top-down proteomic approach, based on the high performance liquid chromatography-electrospray ionization–MS analysis of the intact proteins and peptides, and the qualitative and quantitative profiles were compared with sex- and age-matched control groups. The results showed the following interesting features: 1) as opposed to controls, in Down syndrome subjects the concentration of the major salivary proteins of gland origin did not increase with age; as a consequence concentration of acidic proline rich proteins and S cystatins were found significantly reduced in older Down syndrome subjects with respect to matched controls; 2) levels of the antimicrobial α-defensins 1 and 2 and histatins 3 and 5 were significantly increased in whole saliva of older Down syndrome subjects with respect to controls; 3) S100A7, S100A8, and S100A12 levels were significantly increased in whole saliva of Down syndrome subjects in comparison with controls. The increased level of S100A7 and S100A12 may be of particular interest as a biomarker of early onset Alzheimer''s disease, which is frequently associated with Down syndrome.Down syndrome (DS)1 is a frequent genetic disorder in humans characterized by premature aging (1). A clinical feature of people with DS is the increased prevalence and severity of periodontal disease compared with age-matched subjects of similar levels of intellectual impairment and compared with the general population (2). Common conditions observed in DS are marginal gingivitis, acute and subacute necrotizing gingivitis, advanced periodontitis, gingival recession, and pocket formation (3, 4). It is known that saliva plays an important role in maintaining oral and dental health, because of the presence of a variety of antimicrobial peptides mainly derived from gland secretion, oral epithelial cells, and neutrophils (5). Several papers reported that neutrophils and T-lymphocyte function is impaired in people with DS (6–9). However, the salivary secretion of the antimicrobial LL-37 in young individuals with DS was found normal (10). A review of the literature (11, 12) reveals only sporadic and contradictory reports that attempt to explain the role of saliva in the oral health of subjects with DS, and on the whole, information on the biochemical composition of their saliva is scarce. On the basis of the above information, in the present study, we proposed to investigate the salivary proteome of DS subjects by an intact protein-based “top-down” approach. The spectrum of salivary peptides of DS subjects was compared with that of sex and age-matched healthy control groups to determine qualitative and quantitative differences. Interestingly, the results showed that several members of the S100A family, which possess different biological functions, and also described as potential markers of the Alzheimer Disease, were significantly increased in saliva of Down syndrome subjects with respect to controls. 相似文献
156.
Alessandro Cannavo Giuseppe Rengo Daniela Liccardo Gianluigi Pironti Maria Cecilia Scimia Laura Scudiero Claudio De Lucia Marco Ferrone Dario Leosco Nicola Zambrano Walter J. Koch Bruno Trimarco Giovanni Esposito 《Apoptosis : an international journal on programmed cell death》2013,18(10):1252-1261
The human prothymosin alpha (PTα) gene encodes a 12.5 kDa highly acidic nuclear protein that is widely expressed in mammalian tissues including the heart and importantly, is detectable also in blood serum. During apoptosis or necrosis, PTα changes its nuclear localization and is able to exert an important cytoprotective effect. Since the role of PTα in the heart has never been evaluated, the aim of the present study was to investigate the effects of PTα on cardiomyocytes during ischemic injury. Our data show that seven after myocardial infarction (MI), PTα expression levels are significantly increased both in blood serum and in cardiac tissue, and notably we observe that PTα translocates from the nuclei to cytoplasm and plasma membrane of cardiomyocytes following MI. Furthermore, in vitro experiments in cardiomyocytes, confirm that after 6 h of simulated ischemia (SI), PTα protein levels are upregulated compared to normoxic cells. Importantly, treatment of cardiomyocytes with a recombinant PTα (rPTα), during SI results in a significant decrease in the apoptotic response and in a robust increase in cell survival. Moreover, these effects are accompanied to a significant preservation of the activated levels of the anti-apoptotic serine-threonine kinase Akt. Consistent with our in vitro observation, rPTα-treated MI mice exhibit a strong reduction in infarct size at 24 h, compared to the MI control group and at the molecular level, PTα treatment induces activation of Akt. The present study provides for the first time the demonstration that PTα offers cardioprotection against ischemic injury by an Akt-dependent mechanism. 相似文献
157.
Elena De Falco Gaia Scafetta Chiara Napoletano Rosa Puca Enzo Maria Vingolo Giuseppe Ragona Olga Iorio Giacomo Frati 《Cell and tissue banking》2013,14(2):277-287
Good manufacturing practices guidelines require safer and standardized cell substrates especially for those cell therapy products to treat ocular diseases where fibroblasts are used as feeder layers. However, if these are unavailable for stem cells culturing, murine fibroblasts are regularly used, raising critical issues as accidentally transplanting xenogenous graft and adversely affecting stem cell clinical trials. Moreover, human fibroblasts play a significant role in testing novel ophthalmologic drugs. Accordingly, we developed a standardized laboratory and surgical approach to isolate normal and undamaged Tenon’s fibroblasts to implement the setting up of banks for both stem cells-based ocular cell therapy and in vitro drug testing. A 2–3 cm2 undamaged Tenon’s biopsy was surgically obtained from 28 patients without mutually correlated ocular diseases. Nineteen dermal biopsies were used as control. Fibroblasts were isolated with or without collagenase, cultured in autologous, fetal bovine or AB serum, tested for viability by trypan blue, vimentin expression and standardized until passage 6. Successful Tenon’s fibroblasts isolation was age dependent (P = 0.001) but not sex, pathology or surgery related. A significant rate of successful cultures were obtained when biopsies were not digested by collagenase (P = 0.013). Moreover, cultures in autologous or fetal bovine serum had comparable proliferative properties (P = 0.77; P = 0.82). Through our surgical and laboratory standardized procedure, we elucidated for the first time key points of this human primary culture system, the role of the autologous serum, comparing Tenon’s and dermal fibroblasts. Our protocol may be clinically useful to reduce the risk above mentioned and may be potentially more effective for ophthalmological clinical purposes. 相似文献
158.
Matteo Goldoni Andrea Caglieri Giuseppe De Palma Sonia Longo Olga Acampa Diana Poli 《Biomarkers》2013,18(5):326-339
The aim of this study was to assess and monitor airway exhalation and deposition of particulate matter (PM). After standardizing inspiratory/expiratory flow and volumes, a novel device was tested on a group of 20 volunteers and in a field study on workers exposed to cristobalite. Both male and female subjects showed a higher percentage of deposition in the 0.5?μm channel than in the 0.3?μm channel on a laser particle counter, but it was higher in the males because of their higher exhaled lung volumes. The device was tested on a wider range of particles (0.3–0.5–1.0–2.5?μm) in the cristobalite productive division. The device has low intrasubject variability and good reproducibility, with geometric mean of %CV?5%. Such a measure can be used to assess individual susceptibility to PM, making repeated measures in different environments, and examining the persistence of particles in the airways after a period in polluted environments. 相似文献
159.
Cisgenesis is a genetic modification of a recipient organism with genetic material from a crossable organism. Trying to free cisgenics from the regulatory guidelines of genetically modified organisms (GMOs), some scientists have suggested to classify the genetically modified products by the origin of transferred genes. Aiming at exploring how scientists frame cisgenics in relation to current legal frameworks, we have sent an extensive survey to the totality of researchers working on cisgenics. Trying to provide cisgenics with a new, uncontroversial identity, the respondents present cisgenics as a method of obtaining “natural,” environmentally friendly and economically sustainable crops. However, such strategy is challenged by GMO corporations opposing a segmentation of the sector, and by the opponents of GMOs, who fear that deregulation on cisgenics leads to the deregulation of GMOs. Drawing from the concepts of bio-objectification and bio-identification, we show how the status of this bio-object is likely to remain contested and contestable. 相似文献
160.
Simone Accordini Angelo Guido Corsico Isa Cerveri Leonardo Antonicelli Francesco Attena Roberto Bono Lucio Casali Marcello Ferrari Alessandro Fois Pierpaolo Marchetti Pietro Pirina Roberta Tassinari Giuseppe Verlato Roberto de Marco 《Respiratory research》2013,14(1):16